Handlebar/stem sizes

[iangreenhalgh]

Hi folks

I'm having a problem with the handlebars on my bike build. The original handlebars are flat and I want to replace them with a riser type as I want an upright riding position, none of this leaning forward for my bad back!

I bought a replacement set and the diameter of the part that goes into the stem clamp is too small. So I bought a second replacement set and that's too small as well, same size as the first replacement.

So, before I buy any more parts, I want to know a bit more about these things. I thought all handlebars and stems were the same diameter, clearly not.

If I buy a replacement stem, how do I make sure I'm getting the right diameter?

The difference in diameter is only 2-3mm, is there a way of shimming or similar to make the smaller diameter bars work with the stem I already have?

 

[Ykick]

Fun ain’t it?

All I can suggest: calipers, Sheldon Brown website, calipers, trial & error, calipers….

Seriously, post up some pics and people's memories may be jogged by what you have?

 

[Chalo]

There are four common handlebar-stem interface diameters. 22.2mm is used on BMX bikes and a few beach cruisers. 25.4mm has been the worldwide normal for a long time. 26.0mm is common for drop bars. And 31.8mm is the "new hotness" size to help everyone remember to throw away their old bike and buy a new one.

You're probably faced with having bought a 25.4mm old-and-busted type bar for your new-hotness 31.8mm stem. You can get a bar with a fatter center section, or you can just get a pair of shims to take up the extra room.

Sitting straight up on a bike is bad for your back, because shocks get transmitted straight up your spine. Plus, when sitting straight up, you don't have the mass of your torso positioned as a counterweight to push pedals against. Try a setup that places the bars 3 to 4 inches above saddle level; that's a good compromise between comfort and your ability to use your body while on the bike.

Consider getting a bar with more sweep instead of only more rise. That results in better comfort for most people most of the time.

 

[iangreenhalgh]

Thanks guys, I think you've answered my question. One set of bars I have are for a BMX, the other pair are for a downhill bike, seems they both have the 22.2mm diameter, but I'll have to measure them to be sure, not that I have any calipers but I have a steel rule and eyeballs.

I expect the stem will be 25.4mm, hence the issue.

So it's a set of shims or a new stem.

I think I can make a set of shims out of some aluminium sheet I have lying around.

However, I am thinking that the stem I have places the handlebars a bit too far forward so I might just replace it with a short BMX stem.

On the sweep thing, I was thinking of bending the bars I have a little. When I lived in Holland I rode a traditional Dutch city bike with an upright posture and some highly swept bars like the ones Chalo shows. I liked that.

I'm not too worried about bumps, I have 80/80/16 motorbike tyres on this thing and they cushion out a lot of bumps. Also, I will be using this bike on the road 90% of the time rather than on anything rough and bumpy, but thanks for that info, it's something to bear in mind that I hadn't considered before.

 

[DAND214]

Here's what I did. http://www.amazon.com/Sunlite-Handlebar-Shims-25-4mm-Black/dp/B00629OCTI/ref=cm_wl_huc_item

Dan

 

[Hummina Shadeeba]

31.8 is universal for road and mountain which is really convenient and it's cheap and lighter and very likely stronger as well. Stiffer is a nice thing and it inherently has that. Its been around for awhile now to the point it's rare to find anything else.
Pricepoint.com

I've known a couple people who've broken bars riding and have always kept my ears up to it happening as it scares me badly.
I replace bars after two years when I was racing and riding a lot...but people on electric bikes maybe do as many miles and maybe it's much rougher. A shim is bad idea to me. You can get every shape today in 31.8 for very cheap.

Strap a big piece of styrofoam to your head and your bars snap and you're with you face in you wheel and then SYF

Unless it were an antique steel bar then maybe be worth it but an old aluminum bar ugggh

 

[iangreenhalgh]

The bars I'm using are steel, they ain't snapping, especially as I won't be hurtling down any big hills or rough tracks, just cruising along roads and rural pathways. They are BMX bars, good quality ones so they are pretty tough, albeit rather heavy compared to an aluminium bar.



But I take your point, a shim isn't ideal.

 

[Chalo]

You could use a BMX stem which would fit your bars as intended.

 

[iangreenhalgh]

I could, that is certainly an option. I'm going to shim the stem I have for the time being and might change the stem to a BMX one eventually.

 

[dogman dan]

For bmx bars to mtb stem I just make a shim from some scrap sheet aluminum. Not beer can thin sheet, but thinner than a road sign.

But if the bike is a threaded headset, really easy to just get a stem off a cheap bmx.

 

[spinningmagnets]

If you do end up with a slightly more upright posture, you might consider a suspension seatpost, like the Thudbuster or Suntour NCX...

 

[iangreenhalgh]

Hi Dan

I've made a shim out of thin soft aluminium, I think it's 1.5mm thick, just cut it with a pair of tin snips, took 5 mins and seems to hold them firm. can see me swapping it for a BMX stem eventually though to move the bars roughly 3 inches closer to the seat.

Hi spin

I want a suspension seatpost, I will get one when finances allow. The 80/80/16 tyres I have on this thing seem to cushion out bumps pretty well though. The 80/80/16 motorbike tyre on 20 inch BMX wheel is shown alongside a 26 inch MTB wheel, I have one of these BMX/motorbike wheel combos on both front and back, makes for a semi-fat look and feel and they are very rugged.